Abstracts

RATIONALE: Glutamate is a main excitatory neurotransmitter in the brain and high levels of glutamate have been implicated in causing seizures by activation of N-methyl-D-aspartate (NMDA) receptor. In vivo H1 MRS offers a noninvasive method to measure different brain metabolites levels. MRS measurements of low levels of GABA were previously reported in epileptic patients. Finding of elevated glutamate/glutamine (Glx) level in the brain of epileptic patients may support the mechanism of abnormal Glutamate/GABA balance and suggest specific methods of care. METHODS: The H MRS examinations were performed on three pediatric patients with intractable seizures of different etiologies and on two healthy controls. T2-weighted axial images aquired with a fast spin-echo sequence were used as scout images for MRS data acquisition. Single Voxel proton spectra (voxel size: 2.3-4.1 cc) were collected (TE=40ms, TR=200ms). Resonance peaks of N-acetylaspartate (NAA), total creatine (Cr), Choline-containing compounds (Cho), and Glx were identified and ratios of metabolite/Cr peak areas were calculated as measures of metabolite levels. RESULTS: Glx peak was identified in three patients. Two of the patients had concomitant elevated glutamine levels in plasma and in CSF, in one the data is not available. MRS measurements showed a range of Glx/Cr ratio from 2.3 to 5.3 in all patients compared to 0.7-1.4 in controls. Therapeutic trial with Dextromethorphan (NMDA receptor antagonist) was initiated in one patient with a metabolic disorder. CONCLUSIONS: CSF and serum elevation of glutamate level correlated with the MRS results and with clinical occurence of seizures. NMDA receptor blockage can be considered as a method of treating seizures in pediatric patients. These results may support use of H MRS in the diagnosis and monitoring of the treatment of epilepsy.